How was the base on Pandora built in Avatar?

Question

I understand that ships like the Venture Star were used to bring people to Pandora, but the Venture Star's actual payload is quite small (the fandom page says payload is 350 tons, you can also compare the size of the cargo compartment to the Valkyrie shuttles docked to it, can't be much larger), so there is no way any of the gunships, mech suits, or other heavy equipment such as those colossal mining machines were brought there on Venture Star or other ships like it, let alone the material and components needed to build Hell's Gate to begin with.

Even if everything was manufactured on the planet itself by some sort of 3D printer, there is still no way all the needed material could have been shipped from Earth and they should have been extracted on-site, which should be very difficult and dangerous considering all the aggressive life forms on the planet. So is there any in-universe explanation for how the base was built?

Answer 1

The Venture Star is one of a fleet of ten (or twelve, depending on your preferred source) interstellar ships, each capable of making the journey to Pandora in less than a decade and then returning with hundreds of tonnes of cargo. Additionally, the ISV VS was preceded by other ships that were significantly larger (possibly up to four times larger), allowing thousands tonnes of materiel, weaponry and personnel to be delivered to the surface each year with approximately 1000 tonnes of delivery per annum for multiple decades.

Note also that the initial base was exploratory. It wasn't until the discovery of unobtanium that they shifted the focus to mining operations so there wasn't much of a need for mech-suits and weaponry other than defend scientists leaving the smaller base to test the local environment.

The ISV Venture Star is one of the ten vehicles designed to travel between the Earth and Pandora at maximum acceleration and deceleration to quickly reach (and retreat from) near lightspeed.

_{^{James Cameron's Avatar: An Activist Survival Guide}}

and

ISV Venture Star:
Cargo Capacity: 350 metric tons Pandora to Earth

Cargo, outbound:
1. Universal object-manufacturing system (In-situ Stereolighography plant). This can produce large, complex objects from data describing their three-dimensional form and material composition. Using raw materials obtained on Pandora, construction and mining equipment far too large and massive to be shipped from Earth can be produced, along with any replacement parts that are needed. Smaller items such as weapons and furniture, are also created, using design data brought from Earth. Locally-designed items are made as well, or modifications of existing designs.
2. Micro-miniaturized components like micro- and nanoprocessors and other circuitry elements that cannot be manufactured on Pandora.
3. Data modules. Currently, photochromic glass holographic data-storage cubes are used, each one-centimeter cube containing 100 Petabytes of triply-error-corrected data. Typical imported data includes the specifications for equipment to be manufactured on Pandora.
4. Two Valkyrie shuttlecraft for transfer of personnel and cargo between the orbiting ISV and the surface of Pandora. These vessels are left at Pandora, to replace those from previous missions that have exceeded their design life as manned vehicles. The replaced craft are re-purposed to serve as automated gas harvesters, skimming through Polyphemus’s upper atmosphere to obtain hydrogen and deuterium for refueling the ISV.
5. Developing avatars in amnio tanks.
6. Drugs and other medications that cannot be produced locally.

_{^{Pandorapedia: ISV Venture Star}}

It would seem likely that while the Venture Star is largely equipped to transport people (and return with ore), other vehicles in the fleet can be configured to carry other types of bulk cargo such as vehicles or supplies. It's explicitly noted that the Venture Star's shuttle can transport AMP suits.

The Valkyrie is a single stage-to-orbit (SSTO) transatmospheric vehicle (TAV) with a massive payload capacity. The Valkyrie is roughly four times the size of the twentieth-century Earth shuttles. The Valkyrie and other shuttles in use on Pandora have been hardened to resist pervasive magnetic fields. Its cargo bay can hold troops, AMP Suits, all necessary ammo and gear, plus larger payloads such as specialized lab equipment that cannot be manufactured on Pandora.

_{^{James Cameron's Avatar: An Activist Survival Guide}}

It's also mentioned that the base itself can manufacture a range of useful vehicles, weapons and ammo, obviating the need to ship it from Earth.

In the decades since arrival on Pandora, the RDA has created a proficient on-moon robotic manufacturing facility that takes care of all its vehicle, weapons, and ammunition needs. All weapons are built to with-stand the rigors of Pandora's electromagnetic fields. The various robo-dozers, earth movers, and Slash-Cutters that have decimated the few remaining patches of Terran rainforest also work well. The powerful CARB Weapon System that proved effective in various insurgencies on Earth has now been unleashed on both the creatures of Pandora and on the Na'vi themselves.

_{^{James Cameron's Avatar: An Activist Survival Guide}}

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If you want to, you can even play a part in the early survey missions on Pandora and the discovery of the Na'Vi.

Answer 2

If you note, your link contains a reference to the Venture Star carrying plans for the Hell's Gate stereolithography plant and small components that can't be manufactured on site.

And here's the reference to the plant itself:

Every piece of human machinery used on Pandora must be made at the Stereolithography Plant. Stereolithography is a form of 3D printing which allows the humans to construct practically anything they want as long as they have raw materials. The limited ability of the plant to construct advanced computers is one of the reasons why the humans were not able to use up-to-date technology in their vehicles. If machinery is in need of an update, the blueprints must be brought on an ISV so the plant has a template for the construction. Another thing that must be brought on a starship is some of the more advanced materials used to make the objects, most raw materials are however collected on Pandora.

You start small. After surveying to find a relatively safe place near mineral resources, you send down a small landing party with a prefab base and necessary supplies, including a small 3D printer facility and some robot mining equipment to extract material. All that can be as minimal as a few hundred tons. Then slowly, and over time, you use the small 3D printer plant to build a larger 3D printer plant and larger mining robots and processing equipment. Really no different than a game like Starcraft where you have to balance your development after starting out with minimal resources.

The movie takes place in 2154, and the background indicates that rover exploration of the planet (which would identify useful landing places) began in 2084, 70 years earlier. Humans in person were present for at least 15 years; Augustine arrived in 2139 and began her school for the Na'vi in 2142.

Even if you assume Augustine was one of the first humans on Pandora, leaving minimal time to build Hell's Gate, there's 55 years from the time detailed remote exploration of Pandora began. Even at only 350 tons per trip, the Venture Star by itself could have made 4 round trips between Earth and Pandora in that time, so 1800 tons of supplies. But it isn't, of course, the only ship. That means when humans were ready to make their initial landing, they could have had thousands of tons of supplies already landed by remote at the chosen site or in orbit waiting to be taken down.